Voltage regulator for electrostatic machines



July 9, 935. w. D. COOLIDGE VOLTAGE REGULATOR FOR ELECTROSTATIC MACHINES Filed March 29, 1934 Inventor: William D. Coolidge,

y Himto'rney. 1

Patented July 9,1935 2,007,890"

UNITED STATES PATENT OFFICE VOLTAGE REGULATOR FOR ELECTRO- STATIC MACHINES William D. Coolidge, Schenectady, N. Y., assignor to General Electric Company, a corporation of New York Application March 29, 1934, Serial No. 717,945 12 Claims. 171312) I Mty invention relates to voltage regulators for chine utilizing my improved voltage-regulating elec rostatic machines. device.

With the development of electrostatic machines Referring to the drawing, I have shown an elechaving a relatively high current output, for extrostatic machine I or the general type disclosed ample in the neighborhood of 4 millhamperes at in Patent No. 1,947,220 granted February 13, 1934, 5

one million volts, it has been found feasible to to the General Electric Company on an applicautilize such machines to produce the high volttion of Clifi'ord A. Nickle. This electrostatic maages' frequently required for electrical testing, or chine, which is shown more or less schematically, for exciting electric discharge devices such as coilnprises a chalrgf-accumulating body or high- X-ray tubes. vo age ermina supported on an insulating 10 In using an electrostatic machine to operates. pedestal 3. An endless belt 4 of paper or other vacuum tube it is highly desirable to have some suitable material, which is supported on rollers arrangement for regulating the voltage. An elec- 5 and 6 and driven by an electric motor 1, controstatic machine will in general deliver. to its veys a charge imparted theretoby suitable excithigh-voltage terminal a current which is proporing devices arranged in proximity to roller 6 to 15 tional to the speed at wlliich tletmtafihililie rils drliglen. ililltbl'elt colletcting dlegices arranged inside of If a larger current is de ivere o e is vo age g -vo age ermina Since the inside of the terminal than is being supplied to the load, there terminal is at zero potential, any charge conveyed will be an accumulation of charge thereon and to the collecting devices will flow in any conducta steadily increasing voltage will be built up. A ing-path provided to the outer surface of the 20 state of equilibrium will be reached at an indeterterminal. hr minate high voltage when there is as much cur- For the p pose of illustration, I have shown rent leaving the high-voltage terminal as there is the electrostatic machine for exciting a hot cathentering it. On short circuit the machine will of o e type X-ray t b 3 having a cathode or 1 course deliver no voltage. while on op n c r i ment 9 and an anode Ill. The anode it of the 25 the voltage will rise until the current leaking from X-ray tube is connected between terminal 2 and the high-voltage terminal is eqiiial 1to tlhetgurrent grountc; by ionductorllllia. The X-ray tube has entering the hi h-vol age erm na e maan ou r me allic cap connected to the cathode chine is be u d to Operate ,a vacuum tube 9 and extending into the terminal 2 in contact Operating on full saturation,lthe current flowlnng therewith, whereby the high voltage between terthrou h the tube cannot incr e and the o v minal 2 and ground is applied to the tube. Curvoltage-stabilizing factor will be the current leak: rent for lighting the filament oi the X-ray ma- 8 m the high-voltage terminalchine may be supplied from any suitable source An Obje y invention is to regulate the arranged in suitable relation to the electrostatic volta e of an el ct o a ic i c i lg zi gg machine. For purpczses or illustration, I have 35 the le P m- 8 8 erm shown a storage bat ery l and a variable rein response to the vol a e f the m sistance ll arranged within the high voltage ter- Another object of my invention is to produce a minal of the electrostatic machine for heating voltage regulator for an electrostatic machine the filament 9. comprising a leakage path which carries substan- My voltage regulator comprises in general an 40 tially no current until the voltage of the machine arrangement dependent upon the voltage of an has risen to apredetermmed valum electrostatic machine for varying a leakage path Another object of my invention is to produce so that the lgakagtehcurreint will1 tendltotlprevent a voltage regulator for an electrostatic machine Voltage rise a We e red n 8 which is adjustable over a wide range of opera ticular form of my invention illustrated, the leakmm age path contains a discharge device and an Further objects and advantages of my invention electrostatic shield having its position dependent t th u in d 1 ti upon the voltage of the machine for varying the will become apparen as e o ow g escr p on impedance characteristics of the discharge deproceeds and the features of npvetty which a vice, thereby varying the leakage current. 50

acterize my invention will be pointed out with My voltage'regulator which is shown generally particularity in the claims annexed to and format 3 comprises a leakage path, Circuit,

8 p Of this speclflcfltiontween the terminal 2 and ground including a subnt drawing, the single figure is a perspective stantially spherical metal shell l9 having a cirview, partly in section, of an electrostatic macular opening 20 in the side facing the terminal,

H thumb screw 31 which extends through a nut 38 attached to the shell I9 and is connected to the.

a needle-point electrode 4| arranged in the opening 20 and connected to the shell l9, and a conductor l3 connecting the shell I! to ground.- The shell I8 is suitably supported adjacent the terminal 2 upon a tubular insulating member 2| provided with a base 22; The shell is shaped to prevent corona discharge from taking place at the shell at the normal operating voltage of the electrostatic machine due to the charge induced upon it'by the high voltage terminal 2,- but due to the concentration of the electrostatic field at the point of electrode 4|, a discharge would take place at the point of the electrode at the normal operating voltage of the machine. In order to control the-discharge at the electrode 4 a movable circular disk or shield 23 is provided having an opening 42.through which the electrode 4| may project. The movable shield 23 is arranged in the opening 20- and shields the electrode 4| from the terminal 2, which changes the impedance characteristics of the discharge gap. between the terminal 2' and electrode 4|. The shield 23 is mounted on the end of a rod 24 which is supported by metal ribbons 21 and 28 attached to supporting pieces 29 and 30, secured to the shell IS in any suitable manner, and is movable longitudinally in the direction of the axis of rod 24. A dashpotwhich includes a stationary cylinder 3| attached to the shell I9 and the movable piston 32 attached to the rod 24 is used to damp the iongitudinal movement of the rod 24. A spring 34,

the free. end of which is slotted at 35 to encompass the movable rod 24 is supported at 33 within the shell |9.. The spring bears against a transverse pin 36 in the rod 24 and biases the rod away from the high-voltage terminal 2. The biasing efiect of the spring 34 may be adjusted by a spring 34 at 39. The electrostatic force on the shield 23 tends to move the rod 24 toward the terminal 2 in opposition to the force exerted by the spring 34.

The electrode 4| is connected to the rod 24 by a lever system 40. This lever system comprises a lever 43 pivoted on a fixed pin 44 andhaving one end connected to bar 24 and the other end connected by means of a fork and pin connection to la floating link 45, which is in turn connected by a second fork and pin connection to one end of lever 46 pivoted on a fixed pin 41 and connected to its other end to electrode. It will be obvious that the pivot pins 44 and 41 may be fixedly supported with respect to. shell IS in any suitable manner. Pivot pins 44 and 41 are so located relative to the ends of levers 43 and 46 that when the disk 23 moves to the right, electrode 4| also moves to the right butat a greater speed. Ac-

' cordingly, upon a predetermined movement of disk 23 towardterminal 2, which is caused by a predetermined voltage or charge on the terminal 2, the needle point of electrode 4| will extend far enough through perforation 42, so that a discharge will occur between the terminal 2 and the end of the electrode 4|. The resulting current will tend to prevent further rise in voltage of terminal 2. While I have shown a single needle point 4|, it is of course obvious that a plurality of such needle points with accompanying perforations 42 in disk 23 maybe utilized.

In the operation of the construction which I have described, the filament temperature of tube 8 is first adjusted by means of variable resistance |1 so that the desired current will flow in the tube between the anode Ill and cathode 9. The electrostatic machine is now. started and a voltage begins tobuildup on terminal 2. As the voltage builds up an electrostatic attractive force will be exerted upon disk 23 tending to move the disk toward terminal, 2 against the biasing force of spring 34. When the voltage on terminal 2 becomes suiiiciently great, the electrostatic atminal 2 reaches the voltage for which the regulator has been adjusted, disk 23 will have been moved sufficiently to cause needle ,4| to extend through perforation 42. Disk 23 will then no longer effectively shield point 4|, and a corona discharge will be initiated between the point and the high-voltage terminal. When the corona discharge begins, current will leak from highvoltage terminal 2 to ground by way of conductor |3. The total current leaving terminal 2, that is, the sum of the load current and the leakage current, will now equal the current delivered to terminal 2 by the machine, and the voltage will remain at the desired value. If the voltage of terminal 2 is reduced sufiiciently, the biasing effect of spring 34 will overcome the electrostatic attraction of terminal 2 for disk 23, and rod 24 will move to the left. When needle point 4|, which now also moves to the left but at a greater speed than disk 23, overtakes disk 23, and no longer projects through perforation 42, disk 23 will again become eifective as a shield and the corona discharge will be stopped. It is obvious from the above that the voltage on terminal 2 will be held within the desired range by the movement of needle 4| between shielded and un-' shielded positions. 7

My device may be adjusted for various voltages within a limited range by adjusting the tension of spring 34 by means of thumb screw 31. Further extension of the range of my device may be accomplished by moving pedestal 2| to increase or decrease the distance between the shell l9 and terminal 2.

It will be seen that I have provided a compact, simple regulating device of great flexibility and ease of adjustment. In addition to the obvious simplicity and ease of adjustment of my device, one or the principal advantages over the simple protective spark gap arrangement. lies in the fact that no loss of current will occur until the voltage has risen to the predetermined point.

While I have disclosed a particular embodiment of my invention, I do not desire to be limited to the specific arrangement set forth and I intend in the appended claims to cover all modifications which do not depart from the spirit and scope or my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. An electrostatic machine having a terminal, a voltage regulator for said machine comprising a leakage circuit including a. discharge gap having an electrode in the electrostatic field of said terminal, means shielding said electrode from said field for preventing current flow through said discharge device, and means responsive to the voltage of said terminal and varying the shielding of said electrode for varying the leakage current in said circuit.

2. An'electrostatic machine having a terminal,

a voltage regulator for said machine comprising a leakage circuit including a discharge gap having an electrode in the electrostatic field of said terminal; means shielding said electrode from said field for preventing current flow through said discharge device, and means controlled by said means and moving said electrode to an unshielded position for varying the leakage current in said circuit.

3. An electrostatic machine having a terminal, a voltage regulator for said machine comprising a leakage circuit including a discharge gap having a needle point adjacent said terminal, a shield for said needle point for preventing current flow through said discharge gap, and means producing relative motion said shield and said needle point for varying the impedance characteristics of said discharge gap to vary the leakage current in said circuit.

4. An electrostatic machine having a terminal, a voltage regulator for said machine comprising a leakage circuit including a discharge gap having a needle point adjacent said terminal, a shield for said needle point for preventing current flow through said discharge gap, and means dependent upon the electrostatic forces on said shield and producing relative motion between said shield and said needle point for varying the impedance characteristics of said discharge gap to vary the leakage current in said circuit.

5. An electrostatic machine having a terminal, a voltage regulator for said machine comprising a leakage circuit including a dischargegap having an electrode in the electrostatic field of said terminal, means shielding said electrode from said terminal for preventing current flow through said discharge gap, and means dependent upon the charge on said terminal for moving said electrode to unshielded position to vary the leakage current in said circuit.

6. An electrostatic machine having a terminal, a voltage regulator for said machine comprising a leakage circuit including a discharge gap having an electrode inthe electrostatic field of said terminal, shielding means for said electrode movable and ineii'ective positions for, varying the leakage current in said circuit, and means responsive to the voltage of said terminal for moving said shielding means to either of said two positions.

7. An electrostatic machine having a terminal, a voltage regulator for said machine comprising a leakage circuit including a discharge gap having an electrode adjacent said terminal, means shielding said electrode from said terminal for preventing current flow through said gap, a shield for said discharge gap, said shielding means being movable in response to the electrostatic force exerted by said terminal on said shielding means for varying the shielding of said electrode to vary the leakage current in said circuit, means for biasing said shielding means against movement by said electrostatic force, and means for adjusting said biasing means.

8. An electrostatic machine having a terminal, a voltage regulator for said machine comprising a leakage circuit including a, discharge gap having an electrode adjacent said terminal, a spherical casing adjacent said terminal and having an opening therein presented toward said terminal, a shield arranged in said opening and having an electrode and said shield for moving said electrode in the same direction as said shield but at a greater rate.

9, An electrode for a discharge gap, means for electrostatically shielding said electrode and means responsive to the voltage across the gap and varying the shielding of said electrode for g the impedance characteristics of the gap. 10. A needle point electrode for a discharge electrode, and means dependent upon the voltage across the gap and producing relative motion between said shield and said electrode for varying the impedance characteristics of the gap.

11. An electrode for a discharge gap, a shield for said electrode, said shield being movable in response to the electrostatic force exerted by another electrode of the gap on said shield for varying the impedance characteristics of the gap.

12. A shielded electrode for a discharge gap comprising a spherical casing having an opening adapted to be presented toward another electrode of said gap, a shield arranged in said opening and having an opening therein through which said shielded electrode may project, means responsive to the electrostatic force exerted by the other electrode on said shield for moving said shield, means biasing said shield against movement by said electrostatic force, and means including a lever system connecting said shielded electrode and said shield for moving said shielded electrode in the same direction as said shield but at a greater rate.

WILLIAM D. COOLIDGE. 

